1. Field of the Invention
The present invention relates generally to a liquid crystal display device and, more particularly, to a liquid crystal display device exhibiting a high display performance and a high yield and requiring a small number of manufacturing process steps.
2. Description of the Background Art
A liquid crystal display device generally employed nowadays is constructed such that two glass substrates having electrodes are set in a face-to-face (opposing) relationship, peripheries of these two substrates exclusive of a liquid crystal filling port are fixed by a bonding agent, a liquid crystal is interposed between the two substrates, and the liquid crystal filling port is sealed by a sealing agent. Plastic beads or the like having a uniform particle diameter are dispersed between the substrates as spacers for keeping a fixed distance between these two substrates.
A liquid crystal display device for color display includes color filters R, G and B of colored layers that are disposed on one of the two glass substrates. For instance, a color dot matrix liquid crystal display device of a simple matrix driving includes a Y-substrate having Y-electrodes subjected to band-like patterning in a lateral (Y) direction and an X-substrate having colored layered under the X-electrode subjected to the band-like patterning in a vertical (X) direction, wherein the X- and Y-substrates are provided in an opposing relationship so that the X- and Y-electrodes are substantially orthogonal to each other, and a liquid crystal composition is sealed therebetween. The liquid crystal display device may involve the use of display systems such as, e.g., TN (Twisted Nematic) type, STN (Super Twisted Nematic) type, GH (Guest Host) type, or ECB (Electrically Controlled Birefringence) type and a dielectric liquid crystal. The sealing agent involves the use of, e.g., a bonding agent of a thermosetting type or an ultraviolet ray hardening acrylic or epoxy group.
Furthermore, the color active matrix drive liquid crystal display device is constructed of a TFT array substrate, i.e., an active matrix substrate formed with a switching element, e.g., a thin-film transistor (TFT) with a semiconductor layer composed of amorphous silicon (a-Si), and a pixel electrode, a signal line and a gate line that are connected thereto, and also an opposite substrate disposed in the opposing relationship with the TFT array substrate. The color filters R, G and B are formed on the opposite substrate. Disposed on a screen peripheral portion is a silver paste serving as an electrode transfer member (transfer) for applying a voltage to the opposite substrate from above the active matrix substrate. The two substrates are electrically connected by this electrode transfer member, and the liquid crystal composition is sealed in between those two substrates. Furthermore, polarizing plates are secured on both side of those two substrates.
In the liquid crystal display device using the plastic beads as a spacer, however, alignments of the liquid crystal around the spacers, which are scattered in the liquid crystal between the two substrates, are disordered, resulting in such a problem that the contrast ratio declines due to a leakage of light beams from the spacer peripheral portion. Moreover, the spacers are hard to disperse uniformly and are arranged with ununiformity during a step of dispersing the spacers on the substrate. This results in a display defect, which in turn brings about a decreases in yield.
Under such circumstances, there is proposed a liquid crystal display device using no plastic beads, wherein a pillar-shaped spacer is formed by stacking a plurality of colored layers of color filters on the TFT portion.
Furthermore, it is also proposed that the pillar-shaped spacer composed of the colored layers is disposed on a gate line or signal line among the lines for the active matrix, and that the pillar-shaped spacer is formed on a non-pixel portion by use of a photo resist.
There arises, however, a problem in which, in a liquid crystal display device which is formed by forming pillar-shaped spacers on a color filter substrate and a common electrode are formed on the whole of the substrate including the pillar-shaped spacers, since ITO (Indium Tin Oxide) film as a common electrode is formed at tip and side portions of the pillar-shaped spacers, there occurs a short circuit between the ITO film and wirings/electrodes of the active matrix substrate resulting in display defect.
Moreover, it is difficult to reduce an area size of a non-display area of the liquid crystal display device in terms of arranging the electrode transfer member on the screen peripheral portion.